1. Field of the Invention
The present invention relates to communications networks in general and, in particular, to apparatus and method used to enhance the data management capabilities of devices connected to said network.
2. Prior Art
The description which follows presupposes knowledge of network data communications and switches, network processors, adapters, routers, etc. as used in such communications networks. In particular, the description presupposes familiarity with the OSI model of network architecture which divides network operation into layers. A typical architecture based upon the OSI model of network architecture which divides network operation into layers. A typical architecture based upon the OSI model extends from Layer 1 (also sometimes identified as “L1”) being the physical pathway or from Layer 1 (also sometimes identified as “L1”) being the physical pathway or media through which signals are passed upwards through Layers 2, 3, 4 and so forth to Layer Layer 7, the last mentioned being the layer of applications programming running on a 7, the last mentioned being the layer of applications programming running on a computer system linked to the network. In this document, mention of L1, L2 and so forth is intended to refer to the corresponding layer of a network architecture. The disclosure also presupposes a fundamental understanding of bit strings known as packets and frames in such network communication.
A general model for a communications network may include one or more private networks coupled via a firewall or similar structure to a public network such as the World Wide Web (WWW) better known as the Internet. Communications between devices connected to the network, hereafter called network devices, may occur solely within the private network or through the firewall via the Internet to remote private networks.
In order to exchange information between network devices and to manage the network some type of protocol is required. The protocol could be characterized as a set of rules that govern access to the network and in some cases are used to keep the network in operable condition. Even though there are some standard protocols, such as ethernet, token ring, etc. that can be used on private networks for the most part private network may use any protocol management wishes to use. The only possible restriction is that network devices, on the private network, must be cognizant of the protocol or else the network devices will not be able to operate or communicate satisfactorily.
Because of the lack of uniformity on private protocols further discussion is limited to the public protocol which is used on the internet. The public protocol is referred to as TCP (Transmission Control Protocol)/IP (Internet Protocol). This is a well known protocol which is used to communicate over the internet.
One measure of performance for network devices, such as network processors, running IP routing applications is based upon the number of packets processed or classified within a set time interval such as one second. This in turn can be influenced by the type of classification that is required. For the purpose of routing packets in a network classification may be grouped as Layer 2 (L2), Layer 3(L3), Layer 4(L4) and above. The computational requirements for each of the layers increases from L2 to L4 and above.
For example, L2 classification may be as simple as finding a Media Access Control (MAC) table match. This procedure would require comparing a MAC Source Address (SA) or MAC Destination Address (DA) packet with addresses in a table. A more general approach is to use a Full Match Algorithm, such as the one disclosed in application Ser. No. 09/543531 for L2 classification tasks.
L3 classifications can be used for routing and other L3 functions. L3 classification, if used for routing purposes, requires finding the longest prefix match between information in a packet and information in a database. A Longest Prefix Match Algorithm is used for L3 classification. The Longest Prefix Match Algorithm is more complex than the Full Match Algorithm and, therefore, requires more computational time.
L4 classification includes complex functions such as enforcement of filter rules with possible complex interceding ranges etc. This type of classification usually requires complex algorithm which use relatively long time interval to process a packet. The time interval to process a packet even increases for lookups or classification above L4. Processing above L4 classification is referred to as deep packet processing.
In view of the above, the throughput (number of packets processed per second) of a network device, such as a network processor, depends on the type of lookups or classifications carried out by the device. As a consequence the computational resources of network processors are stressed when L3 and higher lookups are required. In addition, network processors are often required to carry out lookups with millions of packets per second which further stress the computational resources. With the resources of network processors being stressed, the likelihood of them being able to meet throughput requirements and at the same time process L3 and above lookups appears relatively low. Therefore, a need exists for resources which will enable network devices, such as network processors, to maintain throughput to meet performance requirements and at the same time process L3 and above lookups.